ABSTRACT Soil pollution by heavy metals has increased worldwide and the search for plants that can be used to remediate polluted areas is an interesting alternative. The aim of this study was to evaluate the tolerance of tropical grasses to Ni and its availability for the Mehlich 1, DTPA, and USEPA 3051 and 3052 extraction methods in Ni-contaminated Oxisol. Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs ‘Aruana’ and ‘Tanzania’, Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster ‘Xaraés’ and ‘Marandu’, and Urochloa decumbens (Stapf) R.D. Webster ‘Basilisk’ were grown for 90 d in a Typic Hapludox (Oxisol) after adding 20, 40, and 120 mg Ni kg-1 to the soil. Tropical grasses showed a positive response to the application of Ni doses. The order of decreasing tolerance of tropical grasses to Ni in the soil was: ‘Basilisk’ > ‘Xaraés’ > ‘Marandu’ > ‘Aruana’ > ‘Tanzania’ based on the critical toxicity dose. Nickel concentration and accumulation increased with increasing soil Ni doses in all the tropical grasses. Mehlich 1, DTPA, USEPA 3051, and USEPA 3052 Ni extraction methods in the soil are efficient to diagnose Ni availability in tropical grasses.